In the present invention, distribution of adjoining pixels is reflected in density distribution of objective recording pixels so that high quality recording can be conducted. The present invention relates to a color image forming apparatus in which: one pixel image data is divided into small pixels m.times.n (the width.times.the length) considering the adjoining pixel data, and after that, the center of gravity of each line is found; the phase of the reference wave is deviated according to the center of gravity; and dot recording composed of n small scanning lines is conducted by the modulated signal of the pixel density data modulated by the reference wave signal so that a character and a halftone image can be reproduced. The recording apparatus of the present invention is used for a printing apparatus or a displaying apparatus.
In the field of image forming apparatus using an electrophotographic method, a digital halftone image is reproduced in the following manner: an image signal of an original image is read by a scanner; and image density data in which the image signal is gradation-corrected, A/D converted, and shading-corrected, is modulated by a reference signal.
When an original image is read by the scanner, an edge portion of the image is read as halftone density due to the aperture of a solid state image pick-up element installed in the scanner. When a latent image is formed on a photoreceptor with the image density data obtained from the image signal, the image is recorded averagely in a recording pixel corresponding to the edge portion of the latent image in the case where the image density is intermediate, and thereby dot breakage is generated, and as a result, sharpness of the recorded image is lowered. Conventionally, it is widely known that MTF correction for sharpening the image can be conducted by a differential filter, a Laplacian filter, or the like in order to maintain the sharpness of the image. However, this emphasizes only the edge portion of the image, so that uniformity of the halftone image is relatively lowered.
On the other hand, even when an interpolated character or figure is formed from computer graphic (C.G.) data or font data, a similar problem is caused. That is, when the edge portion is interpolated smoothly by the intermediate density of the interpolation data, a recording pixel corresponding to the edge portion is recorded in pixels as average density, and thereby the resolution of the recorded image is lowered.